Anastasia Vashukevich, known by her pen name Nastya Rybka, has been held with several others since a police raid in the sleazy seaside resort of Pattaya last February.
She had travelled to Thailand after becoming embroiled in a political scandal with Russian aluminium tycoon Oleg Deripaska, a one-time associate of US President Trump's disgraced former campaign director Paul Manafort.
She set off a scramble for details after promising to reveal "missing puzzle pieces" regarding claims the Kremlin aided Trump's 2016 election victory.
But the material never surfaced and critics dismissed it as a publicity stunt.
The Pattaya Provincial Court freed her and seven co-defendants after they suddenly pleaded guilty to multiple charges including solicitation and illegal assembly.
"The court found them all guilty of soliciting sex," said a judge on the panel, handing them three-year sentences and $6,000 fines but reducing the sentences to time served.
"The court releases them today," the judge added.
Thai immigration chief Surachate Hakparn said they would be transferred to an immigration detention centre in Bangkok and deported.
"The next step, I will coordinate with the Russian government for their deportation, which will likely take one week for all the processes to complete," Surachate told AFP.
"They are blacklisted from Thailand permanently for conducting bad deeds."
- Seduction guru -
The risque seminar was led by self-styled Russian seduction guru Alex Kirillov and some participants wore shirts that said "sex animator" even though one participant at the time described it as more of a romance and relationship course.
Kirillov, who has served as a spokesperson for the mostly Russian group, told reporters as they arrived as court Tuesday that he believed they were set up.
"I think somebody ordered (our arrest)... for money," he said.
Vashukevich and Kirillov had once expressed fear of being deported back to Russia and at one stage called on Washington for help.
But Vashukevich later blamed the US for their imprisonment.
Both Washington and Moscow publicly had shrugged off Vashukevich's story, which the US State Department described as "bizarre".
A friend of theirs who has been involved in the case and was at the court told AFP that they were "very happy" with Tuesday's verdict.
Vashukevich, who has penned a book about seducing oligarchs, also faces legal problems in Russia.
Deripaska won an invasion of privacy lawsuit against her and Kirillov in July after a video apparently filmed by the model showed the tycoon vacationing with an influential Russian deputy prime minister.
Kremlin-connected Deripaska and Manafort, Donald Trump's ex-campaign manager, did business together in the mid-2000s.
Manafort has since been convicted in the US of financial crimes related to political work he did in Ukraine before the 2016 election as well as witness tampering.
He has also admitted to providing polling data to a Russian with intelligence ties during the 2016 presidential race.